The present invention relates generally to a device for controlling the position of a visual display cursor and further to a method for converting the movement of an object on a surface to electrical signals, and moe particularly, to what is now commonly known as an optical mouse.
A mechanical mouse for user as a peripheral device for the control of a cursor for a visual display in a computer system is well known in the art. Examples of mouse devices known in the prior art can be found in U.S. Pat. Nos. 3,541,521; 3,541,541; 3,835,464; 3,892,963; 3,987,685; 4,303,914; and 4,369,439.
While these devices are useful to aid in the control of a display cursor in response to the movement of a user's hand as the user pushes the mechanical mouse on a pad or a work surface next to the user keyboard, these devices have many disadvantages. Firstly, because they rely on the mechanical movement of a ball or a wheel, they are not particularly reliable because they use many moving parts. A mechanical mouse relies on the rolling action of a ball or wheel on a surface and if the balls or wheels get dirty, they slip on the work surface rather than roll. Moreover, because of the moving parts necessary in the mechanical mouse device, it is relatively expensive compared to the electronics that is contained therein.
In order to overcome the disadvantages of the electromechanical mouse disclosed in the aforementioned prior art patents, an electro-optical mouse has been proposed. Examples of an electro-optical mouse can be found in U.S. Pat. Nos. 4,364,035 and 4,390,873. Another optical mouse has been extensively described in "The Optical Mouse, And An Architectural Methodology For Smart Digital Sensors" Richard F. Lyon, VLSI-81-1 August 1981.
While the optical mouse devices described in the aforementioned two patents and the Lyon article are improvements over the aforementioned mechanical mouse devices, these optical mouse devices disadvantageously require a work surface or pad, which has a defined or predetermined pattern of light and dark areas or colors, in order to operate. The optical mouse then senses the pattern and is able to produce signals representative of the movement of the device relative to the pattern.
The Lyon device, is particularly pattern sensitive, which means, that the internal processing algorithms therein for determining movement, have been defined for the particular predetermined pattern that the optical mouse is to be moved upon and it will only work efficiently on this patterned surface.
While these optical mouse devices are inherently more reliable than electromechanical mouse devices, they have the disadvantage of being pattern sensitive and being operable only on particular patterns that must be located near the workstation keyboard. If these patterns get dirty or otherwise have irregularities in them, the optical mouse devices will not operate efficiently or effectively. Moreover, if for some reason the patterned surface is unavailable to the user, the optical device will become inoperable.